A quick mockup of what iTunes for Yosemite could look like. It's nothing too drastic—just less noise, gradients, and shadows.
I'm unsure if the red/pink color will be used instead of the blue color. While it will match the icon, it may be too much.
This is also only a small part of the UI. I'm unsure how the new Yosemite sidebar background blur will work when the source is also shown as a sidebar (In iTunes 11, View -> Show Sidebar) next to this list of artists.
Maybe Yosemite will get dedicated Music/Videos/Podcasts/iTunes U apps and a new syncing solution for iPod/iPhone (which is not needed as much these days). The only thing holding this back is probably iTunes for Windows support.